DOT compliance with box truck - DE and MD

Hello, I am so in need of help navigating the DOT compliance requirments. I have a small antique store and got a great buy on a box truck-now I know why.. Its a 2003 Chevy Express with a box body, 12000 lbs. dual rear wheels. According the FMCSA, I had to get a DOT code. Once I did that I was bombarded with emails and phone calls about stuff I need to do. this truck gets moved maybe once a month and goes under 20 miles one way. My store is in Delaware but we are only 11 miles from the Maryland state line and go to auctions in Md. We registered the vehicle under the company name and have commercial insurance on it. I'm trying to be compliant, but I don't know what compliant is. I am thinking i need the code, I need a safety inspection and that's it. I would very much appreciate some guidance from the experts.